<template>
  <div>
    <router-link to="/" tag="div" class="header-abs" v-show="showAbs">
      <div class="iconfont  header-abs-back" >&#xe624;</div>
    </router-link>
  <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
     <router-link to="/">
         <div class="iconfont  header-fixed-back" >&#xe624;</div>
     </router-link>
     景点详情
  </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      // 获取当前页面的滚动条纵坐标位置
      // 解决scrollTop 值为0
      // let top = document.documentElement.scrollTop || document.body.scrollTop || window.pageYOffset
      var top = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {
          opacity
        }
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  // 页面展示
  activated () {
    // addEventListener方法用于向指定元素添加事件
    window.addEventListener('scroll', this.handleScroll)
  },
  // 页面被隐藏被替换执行钩子
  deactivated () {
    // removeEventListener 移除 addEventListener方法添加的事件
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
  @import '~stylus/varibles.styl'
  .header-abs
    position: absolute
    left: .2rem
    top: .2rem
    width: .8rem
    height: .8rem
    line-height: .8rem
    text-align: center
    border-radius: .4rem
    background: rgba(0, 0, 0, .8)
    .header-abs-back
      color: #fff
      font-size: .4rem
  .header-fixed
    z-index: 2
    position: fixed
    top: 0
    left: 0
    right: 0
    height: $headerHeight
    line-height: $headerHeight
    text-align: center
    color: #fff
    background: $bgColor
    font-size: .32rem
    .header-fixed-back
      position: absolute
      left: 0
      top: 0
      width: .64rem
      text-align:center
      font-size: .4rem
      color: #fff
</style>
